This invention relates to a marking apparatus used in a process for producing multi-layered printed circuit board.
As electric products are becoming lighter, thinner, shorter, smaller and more functional, which is typically shown in cellular phones, a printed circuit board used in such electric products is also becoming more precise. The multi layered printed circuit board has been developed in this trend, the board is manufactured by a so-called build-up method. The multi layered printed circuit board has a core board, on both back and front faces of which resin isolation layers and conductive patterns made of copper or the like are alternately formed and laminated. The layers are conductive through a hole called a via hole that is plated by copper. The conductive patterns are formed by a lithography method using an aligner having a photo mask that is depicted with an original pattern.
When building up the layers, it is very important to adjust the positions of the layers. The new pattern on a new build up layer must be precisely formed at a certain position relevant to the old pattern on the old layer formed already. To accomplish the alignment between the new and old patterns, an alignment mark depicted on the film mask and a board mark (referred to as a standard mark hereinafter) formed on the board are utilized.
Furthermore, the position of the via-hole must be precisely determined in relation to the unseen pattern formed on a lower layer.
However, the alignment mark on the core board is invisible because the layer is covered by copper foil before the pattern is formed.
Thus the applicant proposed by the Japan Patent laid-open No. 2003-131401 (corresponding to EP1307079A1, U.S. Pat. No. 6,597,757B2 (US2003081719A1), CN1414431A, KR20030035872A, TW545090B) an inventive marking apparatus used in a process for producing multi-layered printed circuit boards with a plurality of insulation layers and patterned conductive layers, having a standard mark that can be detected by X-rays formed on at least one of said layers of said multi-layered printed circuit board, means for irradiating X-rays on an area containing said mark and detecting the position of the mark, and means for making another new mark on an outer layer of said multi-layered printed circuit board based on the position of the standard mark.
In said apparatus, since another alignment mark can be formed on the subsequent outer layers based on the detected mark, it becomes possible to align the news marks to the standard mark. The new alignment mark(s) is typically formed at the position on each layer, corresponding precisely to the detected position of the mark.
However when making the new marks on both side of the board, the front side mark and rear side mark can be made on only the same position in the plane direction (X-Y direction) because the marks are made based on the one same standard mark.
Positioning gaps in a plane direction between the multiple layers can be caused by various reasons in process of making the layers. The conventional marking device uses one standard mark when forming a new mark of the front side and a new mark of the rear side. Thus the positioning gaps of the new marks against the lower layers can arise when the layers have the gaps therebetween in a plane direction.
The object of the invention is to resolve the problem of the conventional marking apparatus.